1. Field of the Invention
The present invention relates to a controlling agent for rice blast.
2. Background Art
Up to now, a large number of active compounds having control effect against various plant diseases have been found, and various controlling agents for plant diseases, comprising them as active ingredients have been developed. For example, from the viewpoint of appearance of resistant strains, however, there is room for improvement in control effect of the controlling agents.
Blast may be mentioned as one of plant diseases, and is induced by infection of fungi of the genus Pyricularia which are a kind of mold fungi and belong to deuteromycotina. In particular, an outbreak of rice blast sometimes takes place in abnormal weather such as low temperature or much rain in the summer period, and, thus, rice blast is one of the most serious diseases of rice.
For this reason, the development of controlling agents having excellent control effect against rice blast has been desired.
International Publication WO 98/55460 discloses 4-quinolinol derivatives and fungicides for agricultural and horticultural applications, comprising these derivatives as active ingredients. In this publication, however, there is no description on usefulness of 2,3-dimethyl-6-t-butyl-8-fluoro-4-quinolinol derivatives.
The present inventors have now found that, among 4-quinolinol derivatives, those having t-butyl (tertiary butyl) at the 6-position and fluorine at the 8-position, that is, 2,3-dimethyl-6-t-butyl-8-fluoro-4-quinolinol derivatives, have significantly high control effect against rice blast. This control effect is significantly superior to that attained by other 4-quinolinol derivatives disclosed, for example, in International Publication WO 98/55460. The present invention has been made based on such finding.
Accordingly, it is an object of the present invention to provide a compound and a controlling agent which have excellent control effect against rice blast.
According to one aspect of the present invention, there is provided a compound of formula (1) or an acid addition salt thereof: 
wherein
R represents a hydrogen atom, xe2x80x94COR1, xe2x80x94COOR1, in which R1 represents alkyl having 1 to 4 carbon atoms, xe2x80x94COCH2OCH3, or xe2x80x94COCH2OCOCH3.
According to another aspect of the present invention, there is provided a controlling agent forrice blast, comprising as active ingredients at least one compound selected from the group consisting of the compounds of formula (1) or acid addition salts thereof.